“Baboons, like people, really do get by with a little help from their friends. Humans with strong social ties live longer, healthier lives, whereas hostility and “loner” tendencies can set the stage for disease and early death.”

“In animals, too, strong social networks contribute to longer lives and healthier offspring—and now it seems that personality may be just as big a factor in other primates’ longevity status.”

“A new study found that female baboons that had the most stable relationships with other females weren’t always the highest up in the dominance hierarchy or the ones with close kin around—but they were the nicest.”

This is better understood by thinking about Self-Interest in the long term,
or as Robert Axelrod put it: by considering The Shadow of the Future,
when we make decisions about whether we cooperate with others or not.